1. Field of the Invention
The present invention relates to a drive and a method for reading data from an information recording medium having a plurality of address regions, and to an information recording medium reproduction apparatus and a method for reproducing data using read error information generated during reading of the data from the information recording medium.
2. Description of the Related Art
An optical disk is known as an information recording medium having a plurality of address regions for storing data. The optical disk has a large capacity and is capable of digitally storing high-quality data. DVDs (Digital Versatile Discs), which have a particularly large capacity among various optical disks, and DVD recording/reproduction apparatuses for recording data into/reproducing information from data stored in the DVDs have been merchandised. The optical disks are expected to store not only computer programs but also real-time data (e.g., AV data) including at least one of sound data and video data. It is anticipated that optical disks used as digital information recording media will be further developed in the future.
At present, as well as an optical disk for reproduction only in which data is recorded by a disk manufacturer in the form of prepits, such as RO-CD and RO-DVD, a recordable optical disk in which a user can record data at home, such as a DVD-RAM, etc., has been developed. Development of an optical disk video recorder which uses DVD-RAMs for recording/reproduction of television broadcasting, or the like, which can be substituted for conventional video tape recorder, such as a VHS recorder, is now proceeding.
For an optical disk in which data can be recorded at high density by non-contact recording, a tracking control technique for allowing laser light to stably follow tracks and lands previously formed in the optical disk, a focus control technique for forming a very small laser spot, and a laser power control technique for achieving a stable output power are required. These control techniques have been demanded to provide control with more accuracy along with the increase in data recording density of the optical disk. These control techniques are used for carrying out systematic recovery processing, whereby stable recording/reproduction can be achieved.
However, it is sometimes impossible to correctly regenerate data from an information recording medium such as an optical disk. Specifically, it may be impossible to correctly read out data due to defects on the optical disk, such as flaws, a fingerprint, etc., or due to defects caused during reading of data. In the case where data recorded in the optical disk is real-time data, the data is generally stored in the form of digital data compressed according to an MPEG format. In this case, a P-picture (Predictive-picture) and a B-picture (Bidirectionally predictive-picture) are predicted based on an I-picture (Intra-picture). Therefore, if data concerning the I-picture used as a reference is not correctly read out, an output image is significantly affected by such incorrectness. Furthermore, data for real-time reproduction, such as real-time data, should be sequentially read out because there is only a little time to carry out a systematic recovery processing.
FIG. 6 schematically shows a conventional information recording medium reproduction apparatus 600. The information recording medium reproduction apparatus 600 includes a drive 610, a host system 630, and a connection bus 620 for connecting the drive 610 and the host system 630. The host system 630 is connected to an output device 640. An optical disk 615 is loaded on the drive 610. The host system 630 includes a data conversion device 635.
In response to a read request from the host system 630, the drive 610 reads data from the optical disk 615. The read data is transmitted to the host system 630 through the connection bus 620. The transmitted data is converted by the data conversion device 635 of the host system 630 and output to the output device 640 such as a television. When the drive 610 reads the data from the optical disk 615, a read error may occur.
FIG. 7 is a flowchart illustrating a conventional data reading method. In this method, when an error occurred during reading of the data, the drive 610 reports to the host system 630 in which address the error occurred.
At the first step of a reading process, the drive 610 receives from the host system 630 a read request to read data from designated address regions (Step 701). In response to the read request, the drive 610 reads the data from the optical disk 615 (Step 702).
In the case where a read error did not occur during the reading of data from the optical disk 615 (Stop 703), the drive 610 reports to the host system 630 that a reading operation from the optical disk 615 has been completed, and transmits the normally read data to the host system 630 (Step 704), thereby terminating the reading process.
Alternatively, in the case where a read error occurred during the reading of data from the optical disk 615 (Step 705), the drive 610 stops a reading operation from the optical disk 615. Then, the drive 610 reports to the host system 630 that the read error occurred and the reading operation has been stopped halfway, and in which address region the error occurred. Then, the drive 610 transmits all of data read from the optical disk 615 to the host system 630 (Step 706), thereby terminating the reading process.
Thus, in this data reading method, in the case where a read error occurred during the reading of data from the optical disk 615, the host system 630 can identify the address region in which the read error occurred and can reproduce information from all of data which had been successfully read out from the optical disk 615 before the error occurred. However, the reading operation stops before all of data has been read from all of the designated address regions.
FIG. 8 is a flowchart illustrating another conventional data reading method. In this method, even when an error occurs during the reading of data, the drive 610 keeps reading data on a real-time basis from the optical disk 615 without reporting to the host system 630 in which address region the error occurred.
At the first step of a reading process, the drive 610 receives from the host system 630 a read request to read data from designated address regions (Step 801). In response to the read request, the drive 610 reads data from the optical disk 615 (Step 802).
In the case where a read error did not occur during the reading of data from the optical disk 615 (Step 803), the drive 610 reports to the host system 630 that a reading operation from the optical disk 615 has been completed, and transmits the normally read data to the host system 630 (Step 807), thereby terminating the reading process.
Alternatively, in the case where a read error occurred during the reading of data from designated address regions in the optical disk 615 (Step 804), the drive 610 determines whether or not the reading of data from all of the designated address regions in the optical disk 615 has been completed without ceasing the reading operation (Step 805). When the reading operation has not completed, the reading operation is restarted from an address region subsequent to the address region in which the read error occurred (Step 806). Then, the steps 802 through 806 are repeated until the reading operation from all of the designated address regions in the optical disk 615 is completed. When the reading operation from all of the designated address regions in the optical disk 615 has been completed (step 805), the drive 610 reports to the host system 630 that the reading operation from the optical disk 615 has been completed, and transmits the read data to the host system 630 (step 807), thereby terminating the reading process.
In this data reading method, the drive 610 continues a reading operation even when a read error occurred, and the host system 630 finally reproduces information from all of the data read from designated address regions. However, according to this data reading methods occurrence of a read error is not reported to the host system 630.
FIG. 9 is a flowchart illustrating a conventional data reproduction method used in the host system 630 which gives a read request to a drive 610 which is controlled by the conventional data reading method described with reference to FIG. 7 or 8. Herein, it is assumed that the host system 630 requests the drive 610 to read real-time data from the optical disk 615. The real-time data is generally recorded in the form of data compressed according to the MPEG format. Therefore, an MPEG decoder is used as a data conversion device 635.
The host system 630 determines a first sector address in the optical disk 615 from which data is to be read out for reproduction, and issues to the drive 610 a read request to read data from designated address regions (Step 901). After issuing the read request to the drive 610, the host system 630 waits to receive a read operation completion signal from the drive 610 which indicates the completion of a reading operation (Step 902). After receiving the read operation completion signal, the host system 630 determines the result of the reading operation of the drive 610 (Step 903).
In the case where an occurrence of a read error is not reported to the host system 630, the host system 630 transmits all of the read data to the decoder 635 which performs MPEG decoding (Step 904).
In the case where data is read out according to the data reading method shown in FIG. 8, even when a read error occurred during the reading of data, the occurrence of the read error is not reported to the host system 630. In this case, incorrect, undecodable data may be transmitted to the decoder 635. Since the decoder 635 attempts to decode such incorrect data but cannot decode correctly, the motion of an output image stops as if it is frozen.
On the other hand, in the case where data is read out according to the data reading method shown in FIG. 7, when a read error occurred during the reading of data, the occurrence of the read error is reported to the host system 630 (Step 903). In this case, a reading operation from the optical disk 615 is stopped due to the read error. The drive 610 transmits only correct data which had been read before the occurrence of the read error except for the data read from an address region in which the read error occurred (Step 905). Then, the host system 630 designates an address region subsequent to the address region wherein the read error occurred, and allows the drive 610 to restart a reading operation from the designated address region (step 906). In this case, since the reading operation is stopped once, data transmission to the decoder 635 is temporarily interrupted.
Data reading from the optical disk 615 and data transmission to the decoder 635 are repeated until the decoder 635 receives all of the data read from the designated address regions in the optical disk 615 according to one of the above-described data reading methods (Step 907).